Gray Wolf Fossil range: Late Pleistocene - Recent
Canis lupus
Conservation status
Least Concern (IUCN 3.1)[1]
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Carnivora Family: Canidae Genus: Canis Species: C. lupus
Binomial name
Canis lupus Linnaeus, 1758
Range map. Green, present; red, former.

The gray wolf (Canis lupus), also known as the timber wolf or wolf, is a mammal of the order Carnivora. The gray wolf is the largest wild member of the Canidae family and an ice age survivor originating during the Late Pleistocene around 300,000 years ago.^[2] Its shoulder height ranges from 0.6 to 0.9 meters (26–36 inches) and its weight varies between 20 (sometimes even lower) and 68 kilograms. DNA sequencing and genetic drift studies indicate that the gray wolf shares a common ancestry with the domestic dog (Canis lupus familiaris) and might be its ancestor.^[3] A number of other gray wolf subspecies have been identified, though the actual number of subspecies is still open to discussion.

Though once abundant over much of North America and Eurasia, the gray wolf inhabits a very small portion of its former range because of widespread destruction of its habitat, human encroachment of its habitat, and the resulting human-wolf encounters that sparked broad extirpation. Considered as a whole, however, the gray wolf is regarded as being of least concern for extinction according to the International Union for the Conservation of Nature and Natural Resources. Today, wolves are protected in some areas, hunted for sport in others, or may be subject to extermination as perceived threats to livestock and pets.

Gray wolves play an important role as apex predators in the ecosystems they typically occupy. Gray wolves are highly adaptable and have thrived in temperate forests, deserts, mountains, tundra, taiga, and grasslands.

Wolves have been featured in the folklore and mythology of many cultures throughout history. Norse mythology tells the legend of the giant Fenrir. More sympathetic depictions include the suckling of Romulus and Remus in the Roman creation story. Wolves have also appeared in Western fairy tales such as Little Red Riding Hood and the Three Little Pigs, in which the wolf plays the role of the villain.

Physiology

Physical characteristics

Wolf weight and size can vary greatly worldwide, tending to increase proportionally with latitude as predicted by Bergmann's Rule. In general, height varies from 0.6 to .95 meters (26–38 inches) at the shoulder and weight ranges from 20 (44 lb.) to 62 (137 lb.) kilograms, which together make the gray wolf the largest of all wild canids.^[4] Although rarely encountered, extreme specimens of more than 77 kg (170 lb.) have been recorded in Alaska, Canada^[5] and Russia.^[6] The heaviest wild wolf on record was killed in post WWII Russian SFSR and weighed 86 kg (189 lb.).^[6] The smallest wolves come from the Arabian Wolf subspecies, the females of which may weigh as little as 10 kg (22 lb) at maturity. Wolves are sexually dimorphic, with females in any given wolf population typically weighing 20% less than males^[7]. They also have narrower muzzles and foreheads, slightly shorter, smoother furred legs and less massive shoulders^[8]. Wolves can measure anywhere from 1.3 to 2 meters (4.5–6.5 feet) from nose to the tip of the tail, which itself accounts for approximately one quarter of overall body length.^[9]

Wolves usually have blended pelages.

Wolves are built for stamina, possessing features ideal for long-distance travel. Their narrow chests and powerful backs and legs facilitate efficient locomotion. They are capable of covering several miles trotting at about a pace of 10 km/h (6 mph), and have been known to reach speeds approaching 65 km/h (40 mph) during a chase.^[10] One female wolf was recorded to have made 7 metre bounds when chasing prey.^[6]

Wolf paws are able to tread easily on a wide variety of terrains, especially snow. There is a slight webbing between each toe, which allows them to move over snow more easily than comparatively hampered prey. Wolves are digitigrade, which, with the relative largeness of their feet, helps them to distribute their weight well on snowy surfaces. The front paws are larger than the hind paws, and have a fifth digit, the dewclaw, that is absent on hind paws.^[11] Bristled hairs and blunt claws enhance grip on slippery surfaces, and special blood vessels keep paw pads from freezing.^[12] Scent glands located between a wolf's toes leave trace chemical markers behind, helping the wolf to effectively navigate over large expanses while concurrently keeping others informed of its whereabouts.^[12] Unlike dogs and coyotes, wolves lack sweat glands on their paw pads. This trait is also present in Eastern Canadian Coyotes which have been shown to have recent wolf ancestry.^[13] Wolves in Israel are unique due to the middle two toes of their paws being fused, a trait originally thought to be unique to the African Wild Dog.^[14]

Wolves molt in late spring or early summer.

Wolves have bulky coats consisting of two layers. The first layer is made up of tough guard hairs that repel water and dirt. The second is a dense, water-resistant undercoat that insulates. The undercoat is shed in the form of large tufts of fur in late spring or early summer (with yearly variations). A wolf will often rub against objects such as rocks and branches to encourage the loose fur to fall out. The undercoat is usually gray regardless of the outer coat's appearance. Wolves have distinct winter and summer pelages that alternate in spring and autumn. Females tend to keep their winter coats further into the spring than males. North American wolves typically have longer, silkier fur than their Eurasian counterparts.^[15]

Fur coloration varies greatly, running from gray to gray-brown, all the way through the canine spectrum of white, red, brown, and black. These colors tend to mix in many populations to form predominantly blended individuals, though it is certainly not uncommon for an individual or an entire population to be entirely one color (usually all black or all white). A multicolor coat characteristically lacks any clear pattern other than it tends to be lighter on the animal's underside. Fur color sometimes corresponds with a given wolf population's environment; for example, all-white wolves are much more common in areas with perennial snow cover. Aging wolves acquire a grayish tint in their coats. It is often thought that the coloration of the wolf's pelage serves as a functional form of camouflage. This may not be entirely correct, as some scientists have concluded that the blended colors have more to do with emphasizing certain gestures during interaction.^[8]

At birth, wolf pups tend to have darker fur and blue irises that will change to a yellow-gold or orange color when the pups are between 8 and 16 weeks old.^[16] Though extremely unusual, it is possible for an adult wolf to retain its blue-colored irises.^[17]

Adolescent wolf with golden-yellow eyes.

Wolves' long, powerful muzzles help distinguish them from other canids, particularly coyotes and golden jackals, which have more narrow, pointed muzzles. Wolves differ from domestic dogs in a more varied nature. Anatomically, wolves have smaller orbital angles than dogs (>53 degrees for dogs compared with <45 degrees for wolves) and a comparatively larger brain capacity.^[18] Larger paw size, yellow eyes, longer legs, and bigger teeth further distinguish adult wolves from other canids, especially dogs. Also, precaudal glands at the base of the tail are present in wolves but not in dogs.

Wolves and most larger dogs share identical dentition. The maxilla has six incisors, two canines, eight premolars, and four molars. The mandible has six incisors, two canines, eight premolars, and six molars.^[19] The fourth upper premolars and first lower molars constitute the carnassial teeth, which are essential tools for shearing flesh. The long canine teeth are also important, in that they hold and subdue the prey. Capable of delivering up to 10,000 kPa (1450 lbf/in²) of pressure, a wolf's teeth are its main weapons as well as its primary tools.^[8] Therefore, any injury to the jaw line or teeth could devastate a wolf, dooming it to starvation and/or incapacity.

Reproduction and life cycle

Usually, the instinct to reproduce drives young wolves away from their birth packs, leading them to seek out mates and territories of their own. Dispersals occur at all times during the year, typically involving wolves that have reached sexual maturity prior to the previous breeding season. It takes two such dispersals from two separate packs for a new breeding pair to be formed, for dispersing wolves from the same maternal pack tend not to mate.^[20] Once two dispersing wolves meet and begin traveling together, they immediately begin the process of seeking out territory, preferably in time for the next mating season. The bond that forms between these wolves often lasts until one of them dies.^[21]

Generally, mating occurs between January and April — the higher the latitude, the later it occurs.^[21] A pack usually produces a single litter unless the alpha male mates with one or more subordinate females. During the mating season, breeding wolves become very affectionate with one another in anticipation of the female's ovulation cycle. The pack tension rises as each mature wolf feels urged to mate. During this time, in fact, the alpha male and alpha female may be forced to prevent other wolves from mating with one another.^[20] Under normal circumstances, a pack can only support one litter per year, so this dominance behavior is beneficial in the long run.

When the alpha female goes into estrus (which occurs once per year and lasts 5–14 days),^[22] she and her mate will spend an extended time in seclusion. Pheromones in the female's urine and the swelling of her vulva make known to the male that the female is in heat. The female is unreceptive for the first few days of estrus, during which time she sheds the lining of her uterus; but when she begins ovulating again, the two wolves mate.

The male wolf will mount the female firmly from behind. After achieving coitus, the two form a copulatory tie once the male's bulbus glandis—an erectile tissue located near the base of the canine penis—swells and the female's vaginal muscles tighten. Ejaculation is induced by the thrusting of the male's pelvis and the undulation of the female's cervix. The two become physically inseparable for anywhere from 10 to 30 minutes, during which the male will ejaculate multiple times.^[23][24] After the initial ejaculation, the male may lift one of his legs over the female such that they are standing end-to-end; this is believed to be a defensive measure.^[24] The mating ritual is repeated many times throughout the female's brief ovulation period, which occurs once per year per female—unlike female dogs, whose estrus usually occurs twice per year.

A wolf resting at the entrance to its den; also note how its coloration blends in with the environment.

The gestation period lasts between 60 and 63 days. The pups, at a weight of 0.5 kg (1 lb), are born blind, deaf, and completely dependent on their mother.^[21][4] There can be anywhere from 1 to 14 pups per litter, with the average litter size being about 4 to 6.^[25] Pups reside in the den and stay there for no longer than two months. The den is usually on high ground near an open water source, and has an open "room" at the end of an underground or hillside tunnel that can be up to a few meters long.^[12] During this time, the pups will become more independent, and will eventually begin to explore the area immediately outside the den before gradually roaming up to a mile away from it at around 5 weeks of age. Wolf growth rate is slower than that of coyotes and dholes.^[26] They begin eating regurgitated foods after 2 weeks of feeding on milk, which in wolves has less fat and more protein and arginine than dog milk.^[7] By this time, their milk teeth have emerged — and are fully weaned by 10 weeks. During the first weeks of development, the mother usually stays with her litter alone, but eventually most members of the pack will contribute to the rearing of the pups in some way.^[21]

After two months, the restless pups will be moved to a rendezvous site, where they can stay safely while most of the adults go out to hunt. One or two adults stay behind to ensure the safety of the pups. After a few more weeks, the pups are permitted to join the adults if they are able, and will receive priority on anything killed, their low ranks notwithstanding. Letting the pups fight for eating privileges results in a secondary ranking being formed among them, and allows them to practice the dominance/submission rituals that will be essential to their future survival in pack life.^[21] During hunts, the pups remain ardent observers until they reach about 8 months of age, by which time they are large enough to participate actively.

Wolves typically reach sexual maturity after two or three years, at which point many of them will be compelled to leave their birth packs and seek out mates and territories of their own.^[21][27] Wolves that reach maturity generally live 6 to 8 years in the wild, although in captivity they can live to twice that age.^[25] High mortality rates give them a low overall life expectancy. Pups die when food is scarce; they can also fall prey to predators such as bears, or, less often, coyotes, foxes, or other wolves. The most significant causes of mortality for grown wolves are hunting and poaching, car accidents, and wounds inflicted while hunting prey. Although adult wolves may be killed by other predators occasionally, rival wolf packs are often their most dangerous non-human enemy. A study on wolf mortality concluded that 14–65% of wolf deaths were inflicted by other wolves.^[28]

Wolves are susceptible to the same infections that affect domestic dogs, such as mange, heartworm, rabies, parvovirus and canine distemper. Epidemics of these can drastically reduce wolf populations in a given area. Wolves are reported to carry over 50 types of parasites, including echinococci, cysticercocci, coeruni (all of which can attack humans) and the trichinellidae family.^[6]

Behavior

Social structure

A pack of Italian wolves at the Parc des Loups.

Wolves function as social predators and hunt in packs organized according to strict, rank-oriented social hierarchies.^[21] It was originally believed that this comparatively high level of social organization was related to hunting success, and while this still may be true to a certain extent, emerging theories suggest that the pack has less to do with hunting and more to do with reproductive success.

The pack is led by the two breeding individuals that sit atop the social hierarchy. The breeding pair has the greatest amount of social freedom compared to the rest of the pack. Although they are not "leaders" in the human sense of the term, they help to resolve any disputes within the pack, have the greatest amount of control over resources (such as food), and have exclusive rights to mating. While most breeding pairs are monogamous, there are exceptions.^[29] An alpha animal may preferentially mate with a lower-ranking animal, especially if the other alpha is closely related (a brother or sister, for example). The death of one breeding wolf does not affect the status of the other, who will quickly take another mate.^[21] Usually, only the breeding pair is able to rear a litter of pups successfully. Other wolves in a pack may breed, but when resources are limited, time, devotion, and preference will be given to the alpha pair's litter. Therefore, non-alpha parents of other litters within a single pack may lack the means to raise their pups to maturity of their own accord. All wolves in a pack assist in raising wolf pups. Some mature individuals choosing not to disperse may stay in their original packs so as to reinforce it and help rear more pups.

After the breeding pair, there may also, especially in larger packs, be a beta wolf or wolves, a "second-in-command" to the alphas. Betas typically assume a more prominent role in assisting with the upbringing of the breeding pair's litter, often serving as surrogate mothers or fathers while the breeding pair is away. Beta wolves are the most likely to challenge their superiors for the role of dominance, though some betas seem content with being second, and will sometimes even let lower ranking wolves leapfrog them for the position of breeding animal should circumstances necessitate such a happening, such as the death of the previous breeding animal. More ambitious beta wolves, however, will only wait so long before contending for breeding position unless they choose to disperse and create their own pack instead.

A wolf pack in Yellowstone National Park, with the alphas leading and the omega in the rear.

Loss of rank can happen gradually or suddenly. An older wolf may simply choose to give way when a motivated challenger presents itself, yielding its position without bloodshed. On the other hand, the challenged individual may choose to fight back with varying degrees of intensity. While the majority of wolf aggression is ritualized and non-injurious, a high-stakes fight can easily result in injury for either or both parties. The loser of such a confrontation is frequently chased away from the pack or, rarely, may be killed as other aggressive wolves contribute to the insurgency. These types of confrontations are more common during the mating season. Deaths occasionally happen, with some dominant male wolves having been known to kill two to four wolves in his lifetime.^[30]

Rank order within a pack is established and maintained through a series of ritualized fights and posturing best described as "ritual bluffing". Wolves prefer psychological warfare to physical confrontations, meaning that high-ranking status is based more on personality or attitude than on size or physical strength. Rank, who holds it, and how it is enforced varies widely between packs and between individual animals. In large packs full of easygoing wolves or in a group of juvenile wolves, rank order may shift almost constantly, or even be circular (for instance, animal A dominates animal B, who dominates animal C, who dominates animal A).

In a more typical pack, only one wolf will assume the role of the omega: the lowest-ranking member of a pack.^[31] Omegas receive the most aggression from the rest of the pack, and may be subjected to different forms of truculence at any time—anything from constant dominance from other pack members to inimical, physical harassment. Submissive individuals are better suited for constant displays of active and passive submission than they are for living alone. Any form of camaraderie is preferable to solitude and, indeed, submissive wolves tend to choose low rank over potential starvation. Despite the aggression to which they are often subjected, omega wolves have also been observed to be among the most playful wolves in the pack, often enticing all of the members in a pack into chasing games and other forms of play. In general, omega wolves exist to help relieve pack tension.

The size of the pack may change over time and is controlled by several factors, including habitat, personalities of individual wolves within a pack, and food supply. Packs can contain between 2 and 20 wolves, though 8 is a more typical size.^[32] New packs are formed when a wolf leaves its birth pack, finds a mate, and claims a territory. Lone wolves searching for other individuals can travel very long distances seeking out suitable territories. Dispersing individuals must avoid the territories of other wolves because intruders on occupied territories are chased away or killed.

Wolves acting unusually within the pack, such as epileptic pups or thrashing adults crippled by a trap or a gunshot, are usually killed by other members of their own pack.^[8]

Body language

See also: Dog communication

This facial expression is defensive and gives warning to other wolves to be cautious.

This facial expression shows fear.

This wolf's submissive posture, wagging tail and horizontal ears show a friendly greeting.

Wolves can communicate visually through a wide variety of expressions and moods ranging from subtle signals, such as a slight shift in weight, to more obvious ones, such as rolling on their backs to indicate complete submission.^[33]

• Dominance – A dominant wolf stands stiff legged and tall. The ears are erect and forward, and the hackles bristle slightly. Often the tail is held vertically and curled toward the back. This display asserts the wolf's rank to others in the pack. A dominant wolf may stare at a submissive one, pin it to the ground, "ride up" on its shoulders, or even stand on its hind legs.
• Submission (active) – During active submission, the entire body is lowered, and the lips and ears are drawn back. Sometimes active submission is accompanied by muzzle licking, or the rapid thrusting out of the tongue and lowering of the hindquarters. The tail is placed down, or halfway or fully between the legs, and the muzzle often points up to the more dominant animal. The back may be partly arched as the submissive wolf humbles itself to its superior; a more arched back and more tucked tail indicate a greater level of submission.
• Submission (passive) – Passive submission is more intense than active submission. The wolf rolls on its back and exposes its vulnerable throat and underside. The paws are drawn into the body. This posture is often accompanied by whimpering.
• Anger – An angry wolf's ears are erect, and its fur bristles. The lips may curl up or pull back, and the incisors are displayed. The wolf may also arch its back, lash out, or snarl.
• Fear – A frightened wolf attempts to make itself look small and less conspicuous; the ears flatten against the head, and the tail may be tucked between the legs, as with a submissive wolf. There may also be whimpering or barks of fear, and the wolf may arch its back.
• Defensive – A defensive wolf flattens its ears against its head.
• Aggression – An aggressive wolf snarls and its fur bristles. The wolf may crouch, ready to attack if necessary.
• Suspicion – Pulling back of the ears shows a wolf is suspicious. The wolf also narrows its eyes. The tail of a wolf that senses danger points straight out, parallel to the ground.
• Relaxation – A relaxed wolf's tail points straight down, and the wolf may rest sphinx-like or on its side. The wolf may also wag its tail. The further down the tail droops, the more relaxed the wolf is.
• Tension – An aroused wolf's tail points straight out, and the wolf may crouch as if ready to spring.
• Happiness – As dogs do, a wolf may wag its tail if in a joyful mood. The tongue may loll out of the mouth.
• Hunting – A wolf that is hunting is tensed, and therefore the tail is horizontal and straight.
• Playfulness – A playful wolf holds its tail high and wags it. The wolf may frolic and dance around, or bow by placing the front of its body down to the ground, while holding the rear high, sometimes wagged. This resembles the playful behavior of domestic dogs.

Howling and other vocalisations

Howling helps pack members keep in touch, allowing them to communicate effectively in thickly forested areas or over great distances. Howling also helps to call pack members to a specific location. Howling can also serve as a declaration of territory, as shown in a dominant wolf's tendency to respond to a human imitation of a "rival" wolf in an area the wolf considers its own. This behavior is stimulated when a pack has something to protect, such as a fresh kill. As a rule of thumb, large packs will more readily draw attention to themselves than will smaller packs. Adjacent packs may respond to each others' howls, which can mean trouble for the smaller of the two. Wolves therefore tend to howl with great care.^[34]

Howling adult wolf on glacial erratic at Little America Flats.

Wolves will also howl for communal reasons. Some scientists speculate that such group sessions strengthen the wolves' social bonds and camaraderie—similar to community singing among humans.^[34] During such choral sessions, wolves will howl at different tones and varying pitches, making it difficult to estimate the number of wolves involved. This confusion of numbers makes a listening rival pack wary of what action to take. For example, confrontation could be disastrous if the rival pack gravely underestimates the howling pack's numbers. A wolf's howl may be heard from up to ten miles away, depending on weather conditions.

Observations of wolf packs suggest that howling occurs most often during the twilight hours, preceding the adults' departure to the hunt and following their return. Studies also show that wolves howl more frequently during the breeding season and subsequent rearing process. The pups themselves begin howling soon after emerging from their dens and can be provoked into howling sessions easily over the following two months. Such indiscriminate howling usually is intended for communication, and does not harm the wolf so early in its life.^[34] Howling becomes less indiscriminate as wolves learn to distinguish howling pack members from rival wolves.

The Middle Eastern and South-East Asiatic wolf subspecies are unusual as they are not known to howl.^[8][35]

Growling, while teeth are bared, is the most visual and effective warning wolves use. Wolf growls have a distinct, deep, bass-like quality, and are often used to threaten rivals, though not necessarily to defend themselves. Wolves also growl at other wolves while being aggressively dominant. Wolves bark when nervous or when they want to warn other wolves of danger but do so very discreetly and will not generally bark loudly or repeatedly as dogs do. Instead they use a low-key, breathy "whuf" sound to immediately get attention from other wolves. Wolves also "bark-howl" by adding a brief howl to the end of a bark. Wolves bark-howl for the same reasons they normally bark. Generally, pups bark and bark-howl much more frequently than adults, using these vocalizations to cry for attention, care, or food. A lesser known sound is the rally. Wolves will gather as a group and, amidst much tail-wagging and muzzle licking, emit a high-pitched wailing noise interspersed with something similar to (but not the same as) a bark. Rallying is often a display of submission to an alpha by the other wolves.^[36] Wolves also whimper, usually when submitting to other wolves. Wolf pups whimper when they need a reassurance of security from their parents or other wolves.

Scent marking

Wolves scent-roll to bring scents back to the pack.

Wolves, like other canines, use scent marking to lay claim to anything—from territory to fresh kills.^[31] Alpha wolves scent mark the most often, with males doing so more than females. The most widely used scent marker is urine. Male and female alpha wolves urine-mark objects with a raised-leg stance (all other pack members squat) to enforce rank and territory. They also use marks to identify food caches and to claim kills on behalf of the pack. Defecation markers are used for the same purpose as urine marks, and serve as a more visual warning, as well.^[31] Defecation markers are particularly useful for navigation, keeping the pack from traversing the same terrain too often and also allowing each wolf to be aware of the whereabouts of its pack members. Above all, though, scent marking is used to inform other wolves and packs that a certain territory is occupied, and that they should therefore tread cautiously.

Wolves have scent glands all over their bodies, including at the base of the tail, between toes, and in the eyes, genitalia, and skin.^[31] Pheromones secreted by these glands identify each individual wolf. A dominant wolf will "rub" its body against subordinate wolves to mark such wolves as being members of a particular pack. Wolves may also "paw" dirt to release pheromones instead of urine marking.^[37]

Hunting and diet

Packs of wolves cooperatively hunt any large herbivores in their range. Pack hunting revolves around the chase, as wolves are able to run for long periods before relenting. It takes careful cooperation for a pack to take down large prey, and the rate of success for such chase is very low. Wolves, in the interest of saving energy, will only chase one potential prey for the first thousand or so meters before giving up and trying at a different time against a different prey.^[38] Therefore, like most other pack species, wolves must hunt continually to sustain themselves. Solitary wolves depend more on smaller animals, which they capture by pouncing and pinning with their front paws. This technique is also common among other canids such as foxes and coyotes.

An American Bison standing its ground, thereby increasing its chance for survival.

Wolves' diets include, but are not limited to, deer, antelope, caribou, moose, yak, and other large ungulates. The American Bison is probably the heaviest animal wolves prey on — bison weighing more than a ton having been taken down by a pack. They also prey on rodents and other small animals in a limited manner, as a typical adult wolf requires a minimum of 1.1 kg (2.5 lb) of food each day for sustenance, and approximately 2.2 kg (5lb) to reproduce successfully.^[25] Wolves rarely eat each day, but compensate by eating up to 10 kg (22 lb) at a time.^[25]

When pursuing large prey, wolves generally attack from all angles, targeting the necks and sides of their prey. Wolf packs test large populations of prey species by initiating a chase, targeting less-fit prey. Such animals typically include the elderly, diseased, and young.^[27] Healthy animals may also succumb through circumstance. However, most healthy, fit individuals will not run from wolves and will instead choose to stand their ground. This defensive technique increases the possibility of injury to the preying wolves. The wolves, not willing to risk injury, are more likely to yield when encountered with such a bold individual. Instead, they will try to target weaker prey members that are easier and safer to hunt. Wolves are generally inefficient at killing large healthy prey, with success rates as low as 20% which is due, in part, to the large size and defensive capabilities of their prey.^[39] Wolves typically kill large prey by tearing at their soft, perinium areas, causing massive bleeding. A single bite can cause a wound up to 10-15 cm in length. A large deer in optimum health will succumb to three bites at the perinium area after a chase of 150 metres.^[6] Though commonly portrayed as targetting solely sick or infirm animals, there is little evidence that they limit themselves to such targets. Research from the former Soviet Union for example shows that in some cases, 93% of all killed prey have no illnesses or infirmities. In the Nenetskij National Okrug, wolves were shown to select pregnant female domestic caribou and calves rather than infirm specimens, with some reports showing that wolves bypassed emaciated, sickly animals in favour of well fed ones.^[6]

Wolves have on occasion been observed to engage in acts of surplus killing. An instance of surplus killing by wolves was witnessed in Canada's Northwest Territories by researchers coming across 34 neonatal caribou calves, scattered over three square kilometres. The wolves had eaten only a few parts from half the calves and not touched the rest. Wolves sometimes only eat a part of their surplus-killed prey, like the tail or the internal organs. However, conditions in nature which favour surplus killing are unusual. Consequently surplus killing in the wild is rare, though fairly common in domestic situations in which the prey animals are usually confined and unable to escape the attackers. ^[40]

Taxonomy

The gray wolf is a member of the genus Canis, which comprises between 7 and 10 species. It is one of six species termed 'wolf', the others being the Red Wolf (Canis rufus), the Indian Wolf (Canis indica), the Himalayan Wolf (Canis himalayaensis), the Eastern Wolf (Canis lycaon) and the Ethiopian Wolf (Canis simensis), although concerning a couple of these there is still some uncertainty as to whether they should be considered subspecies of Canis lupus or species in their own right. Recent genetic research suggests that the Indian Wolf, originally considered only as a subpopulation of the Southern-East Asian Wolf (Canis lupus pallipes), represents a distinct species (Canis indica). Similar results were obtained for the Himalayan wolf, which is traditionally placed into the Tibetan Wolf (Canis lupus laniger) ^[41].

Wolves and coyotes have interbred, producing fertile offspring, a fact which calls into question their status as two separate species.[1]

With respect to common names, spelling differences result in the alternative spelling grey wolf. As the first-named and most widespread of species termed "wolf", gray wolves are often simply referred to as wolves. It was one of the many species originally described by Carolus Linnaeus in his eighteenth-century work, Systema Naturae, and it still bears its original classification, Canis lupus.^[42] The binomial name is derived from the Latin Canis, meaning "dog", and lupus, "wolf".^[43]

Desert dwelling grey wolf subspecies, such as this Arabian wolf, tend to be smaller than their more northern cousins.

Classifying gray wolf subspecies can be challenging. Although scientists have proposed a host of subspecies, wolf taxonomy at this level remains controversial.^[44] Indeed, only a single wolf species may exist. Taxonomic modification will likely continue for years to come.

Current theories propose that the gray wolf first evolved in Eurasia during the early Pleistocene. The rate of changes observed in DNA sequence date the South-East Asiatic lineage to about 800,000 years, as opposed to the American and European lineages which stretch back only 150,000.^[45] The gray wolf then migrated into North America from the Old World, probably via the Bering land bridge (that once joined Alaska and Siberia), around 400,000 years ago. The gray wolf then coexisted with the Dire Wolf (Canis dirus), a Canid species that was larger and heavier than the gray wolf and appeared in South America over 700,000 years ago and whose origin is still speculated. The Dire Wolf ranged from southern Canada to South America until about 8,000 years ago when climate changes are thought to have caused it to become extinct. After that the gray wolf is thought to have become the prime canine predator in North America.

Subspecies

At one point, up to 50 gray wolf subspecies were recognized. Though no true consensus has been reached, this list can be condensed to 13–15 general extant subspecies. Modern classifications take into account the DNA, anatomy, distribution, and migration of various wolf colonies.

Disputed subspecies

Historically, gray wolf classification has been transient in nature. As a result, there still exists some disagreement as to the status of certain possible subspecies. These are listed below.

Transferred subspecies

Extinct subspecies

Disputed species

Relation to the dog

Much debate has centered on the relationship between the wolf and the domestic dog, though most authorities see the wolf as the dog's direct ancestor. Because the canids have evolved recently and different canids interbreed readily, untangling the relationships has been difficult. But molecular systematics now indicate very strongly that domestic dogs and wolves are closely related, and the domestic dog is now normally classified as a subspecies of the wolf: Canis lupus familiaris. The main differences between wolves and domestic dogs are that wolves have, on average, 20% larger brains, better immune systems, a better sense of smell, and are generally larger than domestic dogs.^[46]

Comparative drawing of dog and wolf anatomy by Ernest Thompson Seton. Note the proportionately larger head of the wolf

North American domestic dogs are believed to have originated from Old World wolves. No known dog breed is derived from wolves indigenous to North America. The first people to colonize North America 12,000 to 14,000 years ago brought their dogs with them from Asia, and apparently did not separately domesticate the wolves they found in the New World.^[47]

Interspecific predatory relationships

Wolves typically dominate other canid species in areas where they are sympatric. In North America, wolves are generally intolerant of coyotes in their territory, seeing them as competitors for food and as threats to their cubs; two years after their re-introduction to the Yellowstone National Park, the wolves were responsible for a near 50% drop in coyote populations through both competition and predation. Though smaller in size, coyotes are usually swift enough to escape the jaws of wolves and on some occasions, have even been known to gang up on them.^[48] Near identical interactions have been observed in Greece between wolves and golden jackals.^[49]

The cougar is another predator encountered by the gray wolf in North America. As with the coyote, the gray wolf is usually hostile toward the big cats and will kill cougar kittens if given the opportunity. The wolf's relation to adult cougars is more complex. A pack often takes advantage of cougars, stealing kills and sometimes killing mature adults. Interactions between solitary wolves and cougars are rarer, but the two species have killed each other.^[50] National Park Service cougar specialist Kerry Murphy stated that the cougar usually is at an advantage on a one to one basis, considering it can effectively use its claws, as well as its teeth, unlike the wolf which relies solely on its teeth. Yellowstone officials have reported that attacks between cougars and wolves are not uncommon. Multiple incidents of cougars taking wolves and vice versa have been recorded in Yellowstone National Park. However, researchers in Montana have found that wolves regularly kill cougars in the area, though they did not specify whether or not this was a pack situation.^[51]

Reconstruction of a wolf pack confronting a Grizzly bear by Adolph Murie (1944)

Brown bears are among the few competitors wolves encounter in both Eurasia and North America, while the American black bear is encountered solely in the Americas. The majority of interactions between wolves and bears usually amount to nothing more than mutual avoidance. Serious confrontations depend on a variety of variables, though the most common factor is defence of food and young. Bears will use their superior size to intimidate wolves from their kills and when sufficiently hungry, will raid wolf dens. Wolves in turn have been observed killing bear cubs, to the extent of even driving off the defending mother bears. Deaths in wolf/bear skirmishes are however considered very rare occurrences, the individual power of the bear and the collective strength of the wolf pack usually being sufficient deterrents to both sides.^[52]

In the Russian Far East, the gray wolf's status as an apex predator is challenged by the Siberian tiger. Siberian tigers have been known to prey on wolves and the two species compete for the limited prey base.^[53] Studies have shown that gray wolf populations generally decrease in areas inhabited by the Siberian Tiger.^[54]

In some Middle Eastern countries, the gray wolf will sometimes encounter the striped hyena, mostly in disputes over carcasses. Though not as powerful individually, the gray wolf's social nature usually puts the more solitary hyena at a disadvantage in confrontations.^[55] Wolf remains have been found in cave hyena den sites, though it is unknown if the wolves were killed or scavenged upon.^[56]

In folklore and mythology

Main article: Wolves in folklore, religion and mythology

For more details on this topic, see Werewolf.

Odin watching Tyr feed Fenrir

Humans have a complicated relationship with wolves. In many parts of the world they were a creature to be feared and held in distaste. This was notably accentuated in European folklore beginning in the Christian era. Settlers brought this view with them as they settled North America. The gray wolf, once found in every ecosystem across the Northern Hemisphere, was one of the first species to be culled by settlers. As technology made the killing of wolves and predators easier, humans began to overhunt wolves and cause their numbers to dwindle significantly.

However wolves have also been revered and respected by humans. In Altaic mythology of the Turkic and Mongolian peoples, the wolf is a revered animal. The shamanic Turkic peoples even believed they were descendants of wolves in Turkic legends. The legend of Asena is an old Turkic myth that tells of how the Turkic people were created. In Northern China a small Turkic village was raided by Chinese soldiers, but one small baby was left behind. An old she-wolf with a sky-blue mane named Asena found the baby and nursed him, then the she-wolf gave birth to half wolf, half human cubs therefore the Turkic people were born. Also in Turkic mythology it is believed that a gray wolf showed the Turks the way out of their legendary homeland Ergenekon, which allowed them to spread and conquer their neighbours.^[57][58] In modern Turkey this myth inspired extrme-right nationalist groups known as "Grey Wolves".

The genesis story of the Turks and Mongols is paralleled in the Roman myth of Romulus and Remus, the traditional founders of Rome. The twin babies were ordered to be killed by their great uncle Amulius. The servant ordered to kill them, however, relented and placed the two on the banks of the Tiber river. The river, which was in flood, rose and gently carried the cradle and the twins downstream, where under the protection of the river deity Tiberinus, they would be adopted by a she-wolf known as Lupa in Latin, an animal sacred to Mars.

In Norse mythology, Fenrir or Fenrisulfr is a gigantic wolf, the son of Loki and the giantess Angrboða. Fenrir is bound by the gods, but is ultimately destined to grow too large for his bonds and devour Odin during the course of Ragnarök. At that time he will have grown so large that his upper jaw touches the sky while his lower touches the earth when he gapes. He will be slain by Odin's son, Viðarr, who will either stab him in the heart or rip his jaws asunder according to different accounts. Stories of werewolves can be found in virtually all European countries; these date back from Ancient Greek legend of Lycaon, who in one story was transformed into a wolf as a result of eating human flesh, and the writings of the Roman scholar, Pliny the Elder.^[59]

Many languages have names meaning "wolf". Some examples include, for instance: Scandinavian Ulf, Albanian "Ujk", Hebrew Ze'ev, Hungarian Farkas, Serbian Vuk, Ukrainian Vovk, Romanian Lupescu/Lupulescu and Bulgarian Vǎlko.

In Japan, grain farmers once worshiped wolves at shrines and left food offerings near their dens, beseeching them to protect their crops from wild boars and deer. Talismans and charms adorned with images of wolves protected against fire, disease, and other calamities and brought fertility to agrarian communities and to couples hoping to have children. The Ainu people believed that they were born from the union of a wolflike creature and a goddess.^[60]

Many Chinese proverbs use wolves as a description towards any ill-willed person with a hidden agenda like Wolf hearted (狼子野心) which could also mean a bad person can never be tamed, Wolf heart with a dog lungs (狼心狗肺) refer to an ungrateful person who later betray you after you helped them. There are others proverbs and meaning that refer to the wolf and many of them have a negative connotation.

More familiar still are the fairy tales where the wolf appears as a villain such as in Grimm's Fairy Tales, as well as the Aesopian Fable The Boy Who Cried Wolf.

Current status

Europe

Beginning in the 1970s, Italy began favoring the increase in wolf populations. A new investigation began in the early 1980s, in which it was estimated that there was a growing population of approximately 220-240 animals. New estimates in the 1990s revealed that the wolf populations had doubled, with some specimens taking residence in the Alps — a region not inhabited by wolves for nearly a century. Current estimates indicate that there are 500-600 Italian wolves living in the wild. Their populations are said to be growing at a rate of 7% annually.^[61]

Around 35 wolves in 4 packs are now roaming the heaths of the eastern German region of Lusatia, a region along the German-Polish border, and they are now still expanding their range to the west and north.^[62] Wolves were first spotted in the area back in 1998, and are thought to have migrated from western Poland.^[63] On December 15, 2007, a male wolf was shot illegally in the district of Lüchow-Dannenberg, Lower Saxony.^[64]

Wolves migrated from Italy to France as recently as 1992. The French wolf population is still no more than 40-50 strong, but the animals have been blamed for the deaths of nearly 2,200 sheep in 2003, up from fewer than 200 in 1994. Controversy also arose when, in 2001, a shepherd living on the edge of the Mercantour National Park survived a mauling by three wolves.^[65] Under the Berne Convention, wolves are listed as an endangered species and killing them is illegal. Official culls are permitted to protect farm animals so long as there is no threat to the species.^[66]

In 2001, the Norwegian Government authorized a controversial wolf cull on the grounds that the animals were overpopulated and were responsible for the killing of more than 600 sheep in 2000. The Norwegian authorities scaled back their original plan to kill 20 wolves amid public outcry.^[67] In 2005, the Norwegian government and its Minister of the Environment, Knut Arild Hareide, proposed another cull calling for the extermination of 25 percent of Norway's wolf population. A recent study of the wider Scandinavian wolf population concluded there were 120 individuals at the most, causing great concern regarding the genetic diversity of the isolated population.^[68]

In Russia, government-backed wolf extermination programs have been largely discontinued since the fall of the Soviet Union. As a result, their numbers have stabilized somewhat, though they are still hunted legally. It is estimated that nearly 15,000 of Russia's wolves are killed annually for the fur trade and because of human conflict and persecution. Due to the new capitalist government's focus on economy and other issues plaguing the former communist nation, the study of wolves has been all but abandoned due to lack of funding.^[69] Wolves cross over the border from Russia into Finland on a regular basis. Although they're protected under EU law, Finland has issued hunting permits on a preventative basis in the past, which resulted in the European Commission taking legal action in 2005. In June 2007, the European Court of Justice ruled that Finland had breached the Habitats Directive but that both sides had failed in at least one of their claims.^[70] Finland's wolf population is estimated at around 250.^[70]

The northern and central regions of Belarus are home to perhaps 1,500 to 1,800 wolves. With the exception of specimens in nature reserves, wolves in Belarus are largely unprotected. They are designated a game species, and bounties ranging between €60 and €70 are paid to hunters for each wolf killed. This is a considerable sum in a country where the average monthly wage is €230.^[71]

Though wolf populations have increased in Ukraine, wolves remain unprotected there and can be hunted year-round by permit-holders.^[72]

Bulgaria considers the wolf a nuisance and, like Belarus, has an active wolf bounty.^[73] A project run by the Balkani Wildlife Centre aims to reduce conflict between farmers and wolves by supplying livestock guarding dogs and educating the locals about large carnivores and their role in nature.

According to estimates of experts from the Faculty of Veterinary Medicine in Zagreb, there are 130 to 170 wolves in Croatia and their population is presently stable.^[74] Attitudes are changing in favor of wolves and the animals are now protected under Croatian law ^[75]

Romania has no direct livestock depredation control. However, if complaints about losses get too high, the holder of the hunting rights for the area might apply to kill a higher number of wolves during the winter hunting season. Poaching of carnivores occurs to some degree by means of traps, snares, or poison. The CLCP (Carpathian Large Carnivore Project) has initiated the use of electric fences as an additional tool for overnight livestock protection. The first tests have been very encouraging, with no losses of livestock at all.^[76]

In Slovakia, the 1994 Law on Protection of Nature and Landscape gave wolves full protection, though there is an annual two-month open season between November 1st and January 15th.^[72]

It is thought that there are around 500 to 600 wolves in Poland, mainly in the east.

The current size of the Lithuanian wolf population is said to be composed of 400-500 individuals.^[77]

Asia

There are several hundred wolves in Israel, mostly on the Golan Heights, the Galilee, and the Negev. During the Passover holidays in 2008 a girl was attacked and lightly injured in a campsite in the south. The wolf was kept for a few days to check if he had rabies and then released with a radiotag in Nahal Tze'elim (source: Israel Radio).

China considers wolves a "catastrophe" and claims that they live in only twenty percent of thei